This proposal focuses on chaperone-mediated autophagy (CMA), a catabolic pathway that mediates the selective degradation of cytosolic proteins in lysosomes. CMA contributes to the maintenance of cellular homeostasis by participating in cellular quality control. We have previously found that CMA activity decreases with age and that restoration of proper CMA activity in livers of old rodents prevents organ deterioration and preserves organ function. We propose that failure of CMA contributes to the functional decline characteristic of old organisms and aggravates the course of age-related diseases. The overall goal of this proposal is 1) to identify the causes behind the functional failure of CMA with age, 2) to understand the consequences of the decrease in CMA activity with age in different organs and 3) to explore alternative interventions to the genetic manipulation to enhance CMA activity in aging organisms. With this purpose, during the next period of funding we intend to: 1) determine the contribution of lysosomal chaperones and co-chaperones to the lysosomal internalization of substrate proteins through the CMA translocation complex; 2) elucidate the contribution of CMA to the regulation of cellular lipid metabolism through maintenance of endoplasmic reticulum and lipid droplet homeostasis and 3) analyze the systemic and organ-specific consequences of the decrease in CMA activity with age in relation to the function of this pathway in cellular quality control and in the regulation of the metabolic balance. Significance: This study will elucidate how functional decline of CMA contributes to aging and could help identifying new approaches to correct defective CMA in old organisms and prevent the alterations in cellular and organ homeostasis characteristics of aging